The medical field utilizes highly flexible and torquable catheters and guidewires to perform delicate procedures deep inside the human body. Endovascular procedures typically start at the groin where a catheter and guidewire are inserted into the femoral artery and navigated up to the heart, brain, or other anatomy as required. Once in place, the guidewire is removed so the catheter can be used for the delivery of drugs, stents, embolic devices to treat a variety of conditions, or other devices or agents. The catheter may be a balloon catheter used for therapy directly, either by itself or with a balloon expandable stent pre-loaded on it. A radiopaque dye is often injected into the catheter so that the vessels can be viewed intraprocedurally or in the case of a diagnostic procedure, the dye may be the primary or only agent delivered through the catheter.
Intravascular procedures, by definition, work in and with delicate anatomy, namely the vessels themselves, which are often also compromised by disease. Damage to the vessels is particularly critical to avoid. If blood in the vessels is allowed to “leak,” direct damage can be caused to any tissue outside of the normal capillary approach contacted by the blood, and/or may result in a deadly problem of exsanguination or “bleed out”. When treating an aneurysm, the control of the catheter tip is especially important. An aneurysm is a very fragile ballooned vessel wall which can easily be punctured if the guidewire or catheter is not precisely controlled.
The guidewires and catheters produced with current technology machines (as described in published patents) have limited functionality. An example of such a micro-cutting machine is disclosed in U.S. Pat. No. 6,014,919, issued to Jacobsen et al. on 18 Jan. 2000. Due to the single blade design and other aspects of these existing machines, the machines lack the precision necessary to control small (sub 0.002″) features on a reliable basis. They also lack the ability to precisely control and verify larger features, which could affect the safety and/or performance of these devices. These machines are also only capable of working with electrically conductive stock material because the machines rely on the electrical conductivity of the stock material to determine the position of the stock relative to the cutting blade. Each cut made by the blade into the stock is based on the location of the electromagnetically sensed surface of the stock and the pre-programmed depth of the desired cut. Once a cut is made, the stock piece is rotated 180 degrees, the surface is sensed again, and another pre-programmed cut is made to a desired depth. As the cutting machine is incapable of determining the precise diameter (at the location of the cut) of the stock material being cut, each cut is made according to a preprogrammed depth regardless of that diameter. This is a problem because stock material is not always of a uniform shape and diameter—there are often imperfections along the length of stock that can affect both the roundness of the stock material and the diameter of the stock material at any particular location.
When the stock material is cut in the manner practiced by current cutting machines, a small beam of remaining material, of varying thickness, is formed by the sequential, opposing cuts. This beam is referred to as a resultant beam. If the diameter of the stock is thicker than anticipated at the location of the cuts, then the resultant beam will be thicker and therefore less flexible than desired. If the diameter of the stock is thinner than anticipated at the location of the cuts, then the resultant beam will be thinner and therefore weaker than desired. Thus, the critical dimension that governs both strength (safety) and flexibility (performance) is the width of the resultant beam, which in current micro-cutting machines is not controlled directly and is instead the result of two imprecise measurements—the measure of the relative distance between the blade and the stock material for the first cut and the measure of the relative distance between the blade and the stock material for the second cut. Any imperfection in the surface of the stock material, or inconsistency in the diameter of such material, is directly translated to the resultant beam. This is problematic in terms of both safety and performance of the final product, whether it is a guidewire, catheter or other device. It is especially critical when forming small dimension resultant beams relative to a larger dimension stock material, as an acceptable tolerance relative to the larger diameter of the stock material may be unacceptably large compared to the smaller dimension of the resultant beam. Existing technology is also unable to cut any kind of non-conductive material, such as plastic. The existing cutting machines rely upon electrical conductivity to sense the surface of the material being cut and then make the cuts.
It would therefore be advantageous to create a micro-cutting machine for machining catheters, guidewires and other devices that utilizes two blades to cut both sides simultaneously, that is able to directly control the width of resultant beams, and that is capable of micro-cutting non-conductive material, such as plastic. Such a machine would be faster, more predictable, and more versatile than current micro-cutting machines.